(core) Faster builds all around.

Summary:
Building:
- Builds no longer wait for tsc for either client, server, or test targets. All use esbuild which is very fast.
- Build still runs tsc, but only to report errors. This may be turned off with `SKIP_TSC=1` env var.
- Grist-core continues to build using tsc.
- Esbuild requires ES6 module semantics. Typescript's esModuleInterop is turned
  on, so that tsc accepts and enforces correct usage.
- Client-side code is watched and bundled by webpack as before (using esbuild-loader)

Code changes:
- Imports must now follow ES6 semantics: `import * as X from ...` produces a
  module object; to import functions or class instances, use `import X from ...`.
- Everything is now built with isolatedModules flag. Some exports were updated for it.

Packages:
- Upgraded browserify dependency, and related packages (used for the distribution-building step).
- Building the distribution now uses esbuild's minification. babel-minify is no longer used.

Test Plan: Should have no behavior changes, existing tests should pass, and docker image should build too.

Reviewers: georgegevoian

Reviewed By: georgegevoian

Subscribers: alexmojaki

Differential Revision: https://phab.getgrist.com/D3506

app/server/lib/DocManager.ts

@@ -1,4 +1,4 @@
-import * as pidusage from '@gristlabs/pidusage';
+import pidusage from '@gristlabs/pidusage';
 import {Document} from 'app/gen-server/entity/Document';
 import {getScope} from 'app/server/lib/requestUtils';
 import * as bluebird from 'bluebird';
@@ -27,7 +27,7 @@ import {GristServer} from 'app/server/lib/GristServer';
 import {IDocStorageManager} from 'app/server/lib/IDocStorageManager';
 import {makeForkIds, makeId} from 'app/server/lib/idUtils';
 import {checkAllegedGristDoc} from 'app/server/lib/serverUtils';
-import * as log from 'app/server/lib/log';
+import log from 'app/server/lib/log';
 import {ActiveDoc} from './ActiveDoc';
 import {PluginManager} from './PluginManager';
 import {getFileUploadInfo, globalUploadSet, makeAccessId, UploadInfo} from './uploads';